In a perfect world you could farm loam soils with about 15% clay that were uniformly well drained and where weather conditions during planting and harvesting, always left a window where field operations could be performed on relatively dry soil. Ontario corn producers know that these condition exist for very few and the result is that often our soil has to bear the brunt of operating in less than ideal conditions. Perhaps no one is more sensitive to this problem than Caledonia farmer, Bob Misener. Misener farms heavy clay soils and has been involved in nearly a life long pursuit of creating a low compaction fleet of agricultural equipment.

With support from IFAO, Misener has transformed his grain cart from a rut producing unit, which operated at 94 PSI (i.e.inflation pressure), to a high flotation unit that runs at inflation pressures around 8 PSI (see Table 1). This project focused on lowering the threat of compaction by reducing major factors affecting soil compaction; one is axle load and the second is inflation pressure. Total axle load has continued to rise in nearly all types of agricultural equipment. High axle loads threaten to compact the surface soil, but large tires and high loads can also cause compactive forces to radiate deep into the soil profile, in many cases deeper than most tillage would be performed. As a general rule, soft-sided pneumatic tires exert a force on the soil surface 2-4 PSI more than the inflation pressure. Hence, a reasonable strategy to reduce the potential for soil compaction is to fit running gear that can allow for low inflation pressures. What is a low compaction inflation pressure? This will vary depending on many factors but on average 15 PSI is viewed as a reasonable benchmark. Misener would prefer to see all his gear under 10 PSI.

Progress in knowing axle loads, understanding tire specifications, and adjusting pressure to give you the lowest possible threat of compaction has been greatest on tractors. Towed implements like manure tankers and grain buggies have been notoriously short on tire options that would lessen the potential for rutting. IFAO and Misener took the original grain buggy and made the necessary changes himself to allow for large radial tires to be fitted onto the cart. Going to an equipment dealership and ordering up a low compaction buggy was simply not a possibility.

Misener admits that he farms soils that are very susceptible to soil compaction and that he runs a business where not every field operation can wait until the soil is perfectly fit, but he is a firm believer that every producer should have low compaction as a goal. "Write it on the wall and work towards it." Misener encourages, "it won't happen over night but making equipment decisions with soil sustainability in mind is critical in the long haul."

Getting Started

The critical first steps in reducing compaction risk from running gear:
1) Know the axle loads of your equipment.
2) Dig out the specifications for the tires offered and ask about other options. What does the warranty cover in terms of load, inflation pressure, speed of travel, etc.? What other options are there, you may want to confer with someone specializing in tires?
3) Adjust inflation pressures accordingly. Why run tires at 28 PSI if they are rated for 12 PSI for the job you are doing.